title: Prevalence, distribution, and diversity of Salmonella enterica in a major produce region of California.
abstract: A survey was initiated to determine the prevalence of Salmonella enterica in the environment in and around Monterey County, CA, a major agriculture region of the United States. Trypticase soy broth enrichment cultures of samples of soil/sediment (n = 617), water (n = 252), wildlife (n = 476), cattle feces (n = 795), and preharvest lettuce and spinach (n = 261) tested originally for the presence of pathogenic Escherichia coli were kept in frozen storage and later used to test for the presence of S. enterica. A multipathogen oligonucleotide microarray was employed to identify a subset of samples that might contain Salmonella in order to test various culture methods to survey a larger number of samples. Fifty-five of 2,401 (2.3%) samples yielded Salmonella, representing samples obtained from 20 different locations in Monterey and San Benito Counties. Water had the highest percentage of positives (7.1%) among sample types. Wildlife yielded 20 positive samples, the highest number among sample types, with positive samples from birds (n = 105), coyotes (n = 40), deer (n = 104), elk (n = 39), wild pig (n = 41), and skunk (n = 13). Only 16 (2.6%) of the soil/sediment samples tested positive, and none of the produce samples had detectable Salmonella. Sixteen different serotypes were identified among the isolates, including S. enterica serotypes Give, Typhimurium, Montevideo, and Infantis. Fifty-four strains were sensitive to 12 tested antibiotics; one S. Montevideo strain was resistant to streptomycin and gentamicin. Pulsed-field gel electrophoresis (PFGE) analysis of the isolates revealed over 40 different pulsotypes. Several strains were isolated from water, wildlife, or soil over a period of several months, suggesting that they were persistent in this environment.
authors.affiliation: Produce Safety and Microbiology Research Unit, USDA, Agricultural Research Service, Albany, CA 94710, USA. lisa.gorski@ars.usda.gov
authors.forename: Lisa
authors.initials: L
authors.lastname: Gorski
authors.forename: Craig T
authors.initials: CT
authors.lastname: Parker
authors.forename: Anita
authors.initials: A
authors.lastname: Liang
authors.forename: Michael B
authors.initials: MB
authors.lastname: Cooley
authors.forename: Michele T
authors.initials: MT
authors.lastname: Jay-Russell
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Gordus
authors.forename: E Robert
authors.initials: ER
authors.lastname: Atwill
authors.forename: Robert E
authors.initials: RE
authors.lastname: Mandrell
mesh_terms: D000383:Agriculture; D000818:Animals; D015373:Bacterial Typing Techniques; D002140:California; D002417:Cattle; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects; D005516:Food Microbiology; D005517:Foodborne Diseases / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D015995:Prevalence; D012481:Salmonella Infections, Animal / Q000453:epidemiology*; D019779:Salmonella enterica / Q000235:genetics* / Q000302:isolation & purification* / Q000472:pathogenicity; D012703:Serotyping; D012988:Soil Microbiology; D014871:Water Microbiology